Mikel
看过网上很多关于ASP.NET生成 验证码的东西。大部分都牺牲了一个aspx页面来生成验证码图片。 而且还不利于二次使用。 于是想一直琢磨着想写一个不用牺牲一个aspx页面来完成验证码的控件，在使用的时候只需要引用一个dll并且在工具箱中直接拖到页面上就可。 经过几天努力还真琢磨出来了一个个人认为比较好的方法，于是拿出来共享一下，希望和大家交流交流意见。
现在开始
using System;using System.Collections.Generic;using System.Text;using System.Web;using System.Drawing;using System.IO;using System.Web.SessionState;namespace jdTools.Web
{
public class VerifyImageHttpHandle : IHttpHandler, IRequiresSessionState
{
private string GetRandomNumberString(int codeCount) { int j1; string strChoice = "2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z"; string[] strResult = strChoice.Split(new Char[] { ',' }); string strReturn = ""; Random rnd = new Random(unchecked((int)DateTime.Now.Ticks)); for (int i = 0; i < codeCount; i++) { Random rnd1 = new Random(rnd.Next() * unchecked((int)DateTime.Now.Ticks)); j1 = rnd1.Next(strResult.Length); rnd = new Random(rnd.Next() * unchecked((int)DateTime.Now.Ticks)); strReturn = strReturn + strResult[j1].ToString();
} return strReturn; } private Color GetColor() { return Color.Black; } private Bitmap CreateImage(string str_ValidateCode) { Random newRandom = new Random((int)DateTime.Now.Ticks); int int_ImageWidth = str_ValidateCode.Length * 14; int int_ImageHeight = 20; // 图高20px Bitmap theBitmap = new Bitmap(int_ImageWidth, int_ImageHeight); Graphics theGraphics = Graphics.FromImage(theBitmap); // 白色背景 theGraphics.Clear(Color.White); // 灰色边框 theGraphics.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, int_ImageWidth – 1, int_ImageHeight); int num = theBitmap.Width * theBitmap.Height * 30 / 100; for (int iCount = 0; iCount < num; iCount++) { // 在随机的位置使用随机的颜色设置图片的像素 int x = newRandom.Next(theBitmap.Width); int y = newRandom.Next(theBitmap.Height); int r = newRandom.Next(255); int g = newRandom.Next(255); int b = newRandom.Next(255); Color c = Color.FromArgb(r, g, b); theBitmap.SetPixel(x, y, c); }//for // 10pt的字体 Font theFont = new Font("Arial", 12, FontStyle.Bold); for (int int_index = 0; int_index < str_ValidateCode.Length; int_index++) { string str_char = str_ValidateCode.Substring(int_index, 1); Brush newBrush = new SolidBrush(GetColor()); Point thePos = new Point(int_index * 13 + 1 + newRandom.Next(3), 1 + newRandom.Next(3)); theGraphics.DrawString(str_char, theFont, newBrush, thePos); } theGraphics.Dispose(); return theBitmap; } #region IHttpHandler 成员 public bool IsReusable { get { return true; } } public void ProcessRequest(HttpContext context) { HttpResponse Response = context.Response; // 将生成的图片发回客户端 MemoryStream ms = new MemoryStream(); string NumStr=GetRandomNumberString(5); context.Session.Add("Verify", NumStr); Bitmap theBitmap = CreateImage(NumStr); theBitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); Response.ClearContent(); //需要输出图象信息 要修改HTTP头 Response.ContentType = "image/jpeg"; Response.BinaryWrite(ms.ToArray()); theBitmap.Dispose(); ms.Close(); ms.Dispose(); Response.End(); } #endregion }
}GetRandomNumberString方法用于生成指定个数的随机数字符串。
IHttpHandle接口的ProcessRequest方法可以启用 HTTP Web 请求的处理。
类VerifyImageHttpHandle 继承了IHttpHandle接口用于自定义程序处理的Web请求。然后在web.config的<system.web>节中配置
<httpHandlers> <add verb="*" path="VerifyImg.jd" type="jdTools.Web.VerifyImageHttpHandle"/> </httpHandlers>此时在浏览器中访问VerifyImg.jd时就会得到一个验证码图片，生成验证码的内容就完成了。
现在我们要自定义一个WEB自定义控件。其代码如下：
using System;using System.Collections.Generic;using System.ComponentModel;using System.Text;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;namespace jdTools.Web.UI{ [ToolboxData("<{0}:VerifyImage runat=server></{0}:VerifyImage>")] public class VerifyImage : WebControl { public string Value { get { return HttpContext.Current.Session["Verify"].ToString(); } } public virtual ImageAlign ImageAlign { get { object obj2 = this.ViewState["ImageAlign"]; if (obj2 != null) { return (ImageAlign)obj2; } return ImageAlign.NotSet; } set { if ((value < ImageAlign.NotSet) || (value > ImageAlign.TextTop)) { throw new ArgumentOutOfRangeException("value"); } this.ViewState["ImageAlign"] = value; } } public VerifyImage() : base(HtmlTextWriterTag.Img) { } protected override void AddAttributesToRender(HtmlTextWriter writer) { base.AddAttributesToRender(writer); writer.AddStyleAttribute(HtmlTextWriterStyle.Cursor, "pointer"); writer.AddAttribute("onclick", "this.src='VerifyImg.jd?id='+Math.random()", true); writer.AddAttribute(HtmlTextWriterAttribute.Src, "VerifyImg.jd"); string str2; switch (this.ImageAlign) { case ImageAlign.Left: str2 = "left"; break; case ImageAlign.Right: str2 = "right"; break; case ImageAlign.Baseline: str2 = "baseline"; break; case ImageAlign.Top: str2 = "top"; break; case ImageAlign.Middle: str2 = "middle"; break; case ImageAlign.Bottom: str2 = "bottom"; break; case ImageAlign.AbsBottom: str2 = "absbottom"; break; case ImageAlign.AbsMiddle: str2 = "absmiddle"; break; case ImageAlign.NotSet: str2=""; break; default: str2 = "texttop"; break; } if (str2 != "") writer.AddAttribute(HtmlTextWriterAttribute.Align, str2); } }}VerifyImage 类定义了两个属性。其中Value属性用于取得session中存放的验证码的值。
这里就很简单了，没有必要详说。
在使用的时候aspx页面如下：
<ul> <li>用户名：<asp:TextBox ID="txtUserName" runat="server"></asp:TextBox></li> <li>密 码：<asp:TextBox ID="txtPassWord" runat="server"></asp:TextBox></li> <li>检证码：<asp:TextBox ID="txtVerify" runat="server" Width="50px"></asp:TextBox><jd:VerifyImage ID="verify" runat="server" Height="23px" ImageAlign="AbsMiddle"/></li> </ul>aspx.cs中：
if (txtVerify.Text != verify.Value) { //
.验证码错误 } else { //验证码正确 }
